1. Field of the Invention
The present invention relates to a multi-frequency multi-antenna module, in particular, to a dual-loop antenna and a multi-frequency multi-antenna module for generating good antenna performance.
2. Description of Related Art
Wireless LAN or 802.11a/b/g/n access-point antennas of the prior art are almost of external antenna structure. Common dipole antennas have a plastic or rubber sleeve covering thereon. In general, the dipole antenna is a single-band antenna for 2.4 GHz operation band or a dual-band antenna for 2.4/5 GHz operation band. The height of the dipole antenna is triple the thickness of the wireless broadband router/hub device, and one part of the dipole antenna is disposed on a side of the router and the rest of the dipole antenna is protruding from the top housing of the router. However, the protruded part of the dipole antenna can easily be vandalized by outside force and also occupies space, which deteriorates the aesthetic appeal of the product, especially for the multi-antenna system.
However, the above-mentioned prior art has the following common defects: 1. The traditional dipole antenna needs to use the plastic or rubber sleeve covering around the antenna, so that the cost is increased; 2. The antenna of the prior art cannot be fully hidden in the router, so that the aesthetic appeal of the product that uses the antenna of the prior art is deteriorated.
In addition, when 2.4/5.2/5.8 GHz wireless LAN or 802.11a/b/g/n wireless standards are applied to a built-in antenna design, the design of the antenna can be chosen from a PIFA antenna, a shorted-monopole antenna or a patch antenna. In general, the maximum antenna gains of the built-in PIFA antenna or shorted-monopole antenna are about 3 dBi and 4 dBi at 2.4 GHz and 5.2/5.8 GHz band, respectively. And the broadside radiation of the radiation pattern is much less common in the PIFA antenna or shorted-monopole antenna. It is necessary to use the patch antenna or the microstrip antenna in order to achieve high gain antenna (the maximum antenna gain needs to be over at least 6 dBi at 2.4 GHz and 5.2/5.8 GHz bands). Because the radiation pattern of the patch antenna or microstrip antenna is broadside radiation that can show directive radiation pattern, the maximum antenna gain of the patch antenna or microstrip antenna is larger than that of the PIFA antenna or shorted-monopole antenna. However, the patch antenna or microstrip antenna is composed of two structure layers, one structure layer is an antenna radiating body and another structure layer is an antenna grounding plane. In addition, the antenna radiating body needs to occupy a lot of space, and the patch antenna or microstrip antenna is an unbalanced structure, so that the patch antenna or microstrip antenna is affected easily by effects of grounding plane.